Device and method for controlling a fuel-oxidizer mixture for a premix gas burner

Abstract

A device for controlling a fuel-oxidizer mixture for a premix gas burner includes: an intake duct, including an inlet, a mixing zone, and a delivery outlet; an injection duct; a gas regulating valve, located along the injection duct; a fan, located in the intake duct to generate therein a flow of the oxidizer fluid or of the mixture; a control unit, configured for generating drive signals; a sensor unit, configured to detect a first differential pressure, between a first detecting section, located in the intake duct upstream of the mixing zone in the direction of inflow and a second detecting section, located in the intake duct downstream of the mixing zone in the direction of inflow, and configured to detect a second differential pressure, between the first detecting section and a third detecting section, located in the injection duct between the gas regulating valve and the mixing zone.

What is claimed is: 
     
         1 . A device for controlling a fuel-oxidizer mixture for a premix gas burner, comprising:
 an intake duct, which defines a section for the admission of an oxidizer fluid into the duct and includes an inlet for receiving the oxidizer, a mixing zone for receiving the fuel and allowing it to be mixed with the oxidizer, and an outlet for delivering the mixture to the burner;   an injection duct, which defines a section for the admission of the fuel and which is connected to the intake duct in the mixing zone to supply the fuel;   a gas fuel regulating valve, located along the injection duct;   a fan, located in the intake duct to generate therein a flow of the oxidizer fluid or of the fuel-oxidizer mixture in a direction of inflow oriented from the inlet to the delivery outlet;   a control unit, configured for generating drive signals, for regulating the gas regulating valve and the rotation speed of the intake fan;   a sensor unit, in communication with the control unit and configured for detecting
 a first differential pressure, between a first detecting section, located in the intake duct upstream of the mixing zone in the direction of inflow and a second detecting section, located in the intake duct downstream of the mixing zone in the direction of inflow, and 
 a second differential pressure, between the first detecting section and a third detecting section, located in the injection duct between the gas regulating valve and the mixing zone; and 
   a mixer, located along the intake duct, at the mixing zone, wherein the sensor unit is associated with the mixer, wherein the mixing zone is positioned upstream or downstream of the fan, the mixer comprising   a first through cavity, open onto the first detecting section;   a second through cavity, open onto the second detecting section; and   a third through cavity, open onto the third detecting section;
 wherein the sensor unit comprises a first pressure connection, a second pressure connection and a third pressure connection, which are located inside the first, second and third through cavities, respectively. 
   
     
     
         2 . The device according to  claim 1 , wherein the sensor unit comprises:
 a first sensor, including a respective pressure connection for the first detecting section and a respective pressure connection for the second detecting section, and a second sensor, including a respective pressure connection for the first detecting section and a respective pressure connection for the third detecting section, or   a single sensor, including a pressure connection for the first detecting section, a pressure connection for the second detecting section, and a pressure connection for the third detecting section.   
     
     
         3 . The device according to  claim 1 , wherein the control unit is programmed for:
 commanding a predetermined flow rate variation by regulating the fan or the gas regulating valve;   detecting a first variation, representing a variation in the first differential pressure due to the predetermined flow rate variation;   detecting a second variation, representing a variation in the second differential pressure due to the predetermined flow rate variation; and   performing a diagnosis of the sensor unit based on the first and the second variation.   
     
     
         4 . The device according to  claim 3 , wherein the control unit is programmed for:
 comparing the first variation with a first predetermined variation; and   comparing the second variation with a second predetermined variation, the first and the second predetermined variation being associated with the predetermined flow rate variation.   
     
     
         5 . The device according to  claim 3 , wherein the control unit is programmed for:
 determining a first trend, representing the fact that the first variation is positive or negative;   determining a second trend, representing the fact that the second variation is positive or negative;   comparing the first trend with the second trend, to check that the first and the second variation are both positive or both negative; and   generating a notification of possible fault if the first and the second variation have opposite signs.   
     
     
         6 . The device according to  claim 1 , wherein the sensor unit comprises a first pressure connection, a second pressure connection and a third pressure connection, in fluid communication with the first detecting section, the second detecting section and the third detecting section, respectively, and wherein the first differential pressure is measured across the first pressure connection and the second pressure connection, and the second differential pressure is measured across the first pressure connection and the third pressure connection. 
     
     
         7 . A method for controlling a fuel-oxidizer mixture in a premix gas burner, comprising the following steps:
 generating an air flow, by means of a fan, in an intake duct including an inlet for receiving the oxidizer, a mixing zone, and an outlet for delivering the mixture to the burner;   feeding fuel to the mixing zone through an injection duct;   mixing the oxidizer and the fuel in the mixing zone;   regulating the fuel flow rate through a gas regulating valve;   generating drive signals through a control unit and sending the drive signals to the gas regulating valve and to the fan;   detecting a first differential pressure, between a first detecting section, located in the intake duct upstream of the mixing zone in the direction of inflow and a second detecting section, located in the intake duct downstream of the mixing zone in the direction of inflow;   detecting a second differential pressure, between the first detecting section and a third detecting section, located in the injection duct between the gas regulating valve and the mixing zone;   providing a first pressure connection, a second pressure connection and a third pressure connection; and   inserting the first pressure connection, the second pressure connection and the third pressure connection into a first, a second and a third through cavity of the mixer, respectively,   wherein the first, the second and the third through cavity are open onto the first detecting section, the second detecting section and the third detecting section, respectively.   
     
     
         8 . The method according to  claim 7 , comprising a step of diagnosing, including the following steps, performed by a processor of the control unit:
 commanding a predetermined flow rate variation by regulating the fan or the gas regulating valve;   detecting a first variation, representing a variation in the first differential pressure due to the predetermined flow rate variation;   detecting a second variation, representing a variation in the second differential pressure due to the predetermined flow rate variation; and   performing a diagnosis of the sensor unit based on the first and the second variation.   
     
     
         9 . The method according to  claim 8 , wherein the step of diagnosing comprises the following steps:
 comparing the first variation with a first predetermined variation; and   comparing the second variation with a second predetermined variation, the first and the second predetermined variation being associated with the predetermined flow rate variation.   
     
     
         10 . The method according to  claim 7 , wherein the step of diagnosing comprises a step of diagnosing with the burner off, comprising the following steps:
 generating drive signals, representing a predetermined rotation speed of the fan, corresponding to a predetermined flow rate and/or pressure;   detecting, through the sensor unit, a value of the first differential pressure and of the second differential pressure, responsive to the predetermined flow rate;   sending the value of the first differential pressure and of the second differential pressure to the control unit;   comparing, in the control unit, the first differential pressure and the second differential pressure with respective reference data representing reference values of the first predetermined differential pressure and of the second predetermined differential pressure for the specific flow rate set by the control unit; and   diagnosing the operation of the first and the second sensor based on the comparison of the first differential pressure and the second differential pressure, detected by the sensor unit, with the reference data.   
     
     
         11 . The method according to  claim 8 , wherein the step of diagnosing comprises the following steps:
 determining a first trend, representing the fact that the first variation is positive or negative;   determining a second trend, representing the fact that the second variation is positive or negative;   comparing the first trend with the second trend, to verify that the first and the second variation are both positive or both negative; and
 generating a notification of possible fault if the first and the second variation have opposite signs. 
   
     
     
         12 . The method according to  claim 7 , wherein the method comprises a step of providing a mixer, mounted along the intake duct at the mixing zone and a step of connecting the sensor unit to the mixer. 
     
     
         13 . The method according to  claim 7 , wherein the method comprises a step of providing a first pressure connection, a second pressure connection and a third pressure connection, in fluid communication with the first detecting section, the second detecting section and the third detecting section, respectively, and wherein the first differential pressure is measured across the first pressure connection and the second pressure connection, and the second differential pressure is measured across the first pressure connection and the third pressure connection. 
     
     
         14 . The method according to  claim 7 , comprising the following steps:
 receiving a flame signal representing the presence of a flame deriving from the combustion of a fuel belonging to a first predetermined type or a second predetermined type inside a combustion cell of the burner; and   accessing fuel data, representing the fact that the gas fuel belongs to the first type or the second type;   wherein the processor has access to a memory unit containing first regulation data and second regulation data, different from the first regulation data and is programmed to generate the drive signals based on the first regulation data or, alternatively, on the second regulation data, depending on the fuel data.   
     
     
         15 . The method according to  claim 7 , comprising an additional step of diagnosing, including the following steps, performed by a processor of the control unit:
 detecting a temperature in the combustion cell;   comparing the detected temperature value with one or more limit values; and   
       compensating a reading of the sensor unit based on the preceding step of comparing. 
     
     
         16 . A device for controlling a fuel-oxidizer mixture for a premix gas burner, comprising:
 an intake duct, which defines a section for the admission of an oxidizer fluid into the duct and includes an inlet for receiving the oxidizer, a mixing zone for receiving the fuel and allowing it to be mixed with the oxidizer, and an outlet for delivering the mixture to the burner;   an injection duct, which defines a section for the admission of the fuel and which is connected to the intake duct in the mixing zone to supply the fuel;   a gas fuel regulating valve, located along the injection duct;   a fan, located in the intake duct to generate therein a flow of the oxidizer fluid or of the fuel-oxidizer mixture in a direction of inflow oriented from the inlet to the delivery outlet;   a control unit, configured for generating drive signals, for regulating the gas regulating valve and the rotation speed of the intake fan;   a sensor unit, in communication with the control unit and configured for detecting
 a first differential pressure, between a first detecting section, located in the intake duct upstream of the mixing zone in the direction of inflow and a second detecting section, located in the intake duct downstream of the mixing zone in the direction of inflow, and 
 a second differential pressure, between the first detecting section and a third detecting section, located in the injection duct between the gas regulating valve and the mixing zone, 
   wherein the control unit is programmed for:   commanding a predetermined flow rate variation by regulating the fan or the gas regulating valve;   detecting a first variation, representing a variation in the first differential pressure due to the predetermined flow rate variation;   detecting a second variation, representing a variation in the second differential pressure due to the predetermined flow rate variation; and   performing a diagnosis of the sensor unit based on the first and the second variation.   
     
     
         17 . The device according to  claim 16 , wherein the control unit is programmed for
 determining a first trend, representing the fact that the first variation is positive or negative;   determining a second trend, representing the fact that the second variation is positive or negative;   comparing the first trend with the second trend, to check that the first and the second variation are both positive or both negative; and   generating a notification of possible fault if the first and the second variation have opposite signs.   
     
     
         18 . A method for controlling a fuel-oxidizer mixture in a premix gas burner, comprising the following steps:
 generating an air flow, by means of a fan, in an intake duct including an inlet for receiving the oxidizer, a mixing zone, and an outlet for delivering the mixture to the burner;   feeding fuel to the mixing zone through an injection duct;   mixing the oxidizer and the fuel in the mixing zone;   regulating the fuel flow rate through a gas regulating valve;   generating drive signals through a control unit and sending the drive signals to the gas regulating valve and to the fan;   detecting a first differential pressure, between a first detecting section, located in the intake duct upstream of the mixing zone in the direction of inflow and a second detecting section, located in the intake duct downstream of the mixing zone in the direction of inflow; and   detecting a second differential pressure, between the first detecting section and a third detecting section, located in the injection duct between the gas regulating valve and the mixing zone,   wherein the method further comprises a step of diagnosing, including the following steps, performed by a processor of the control unit:   commanding a predetermined flow rate variation by regulating the fan or the gas regulating valve;   detecting a first variation, representing a variation in the first differential pressure due to the predetermined flow rate variation;   detecting a second variation, representing a variation in the second differential pressure due to the predetermined flow rate variation; and   performing a diagnosis of a sensor unit based on the first and the second variation.